1. Field of the Invention
The present invention relates to a ceramic material in particular to perovskite type ceramic for use in the manufacturer of ion and/or electron conducting ceramic products.
2. Description of the Related Art
Peroskite ceramic materials for use in oxygen separation membranes, having the general formula: EQU A.sub.x A'.sub.x' A".sub.x" B.sub.y B'.sub.y' B".sub.y" O.sub.3-.delta.,
wherein
x+x'+x"=1, and PA1 y+y'+y"=1, and PA1 -1&lt;.delta.&lt;1 PA1 A, A' and A" each is one or more metals selected from the group of lanthanide metals; PA1 B, B' and B" each is a metal selected from the group of sodium alkaline earth metals transition metals, group 3a, and noble metals of group 8b; PA1 x+x'+x"&lt;1 and/or y+y'+y"&lt;1 PA1 such that .SIGMA.x.sub.i .noteq..SIGMA.y.sub.i.
are known from U.S. Pat. No. 5,240,473.
The ceramic materials of the above US Patent have a stoichiometric perovskite composition, wherein .SIGMA.x.sub.i and .SIGMA.y.sub.i are 1.
It has been found by the present inventors that non-stoichiometric perovskite type ceramic materials, wherein .SIGMA.x.sub.i and/or .SIGMA.y.sub.i are less than 1, show an unexpectedly improved stability and reduced reactivity with metals or metal oxides supported on or otherwise combined with the ceramic material.
Furthermore, it has been proved by the present inventors that A-side deficits induce an increased electronic and ionic conductivity due to an increased defect concentration in the material.